Studies of vegetation, fire and climate dynamics during the late Quaternary as contribution towards conservation and management of the
biodiversity hotspot „Mata Atlântica“ in southern Brazil
PhD Thesis
submitted
at the Georg August University Göttingen, Faculty of Biology
for the degree “Doctor of Philosophy (PhD) /Dr. rer. nat.”
in the Georg-August-University School of Science (GAUSS) Program
by
Vivian Luciana Jeske-Pieruschka
born in Curitiba, Brazil
Göttingen 2011
Supervisor: Prof. Dr. Hermann Behling
Albrecht-von-Haller-Institute for Plant Sciences Department of Palynology and Climate Dynamics University of Göttingen
Untere Karspüle 2
37073 Göttingen – Germany
Co-supervisor: Prof. Dr. Erwin Bergmeier
Albrecht-von-Haller-Institute for Plant Sciences Department of Vegetation & Phytodiversity Analysis University of Göttingen
Untere Karspüle 2
37073 Göttingen – Germany
Date of oral exam: 20/01/2011
To my lovely partner Marius and My dear parents Fredo and Erica
i Table of Content
Acknowledgments ……… iv
Preface ……….. v
Chapter One – Introduction ……… 1
1.1. The Atlantic Forest Biome ……… 2
1.2. Previous studies on the ecosystems of the Atlantic Forest Biome in southern Brazil during the late Quaternary ……… 4
1.3. Aims of the work ………. 5
1.4. Study region ……… 7
1.4.1. Location of the study sites ……….. 7
1.4.2. Geomorphology and soil ………. 9
1.4.3. Climate ……….. 10
1.4.4. Current distribution of the vegetation ……… 11
1.5.Methods ….……… 13
1.5.1. Fieldwork ………...………. 13
1.5.2. Analyzed sediment cores …….………...…… 14
1.5.3. Laboratory techniques ………...……….. 17
1.5.4. Identification of pollen and spores ………. 18
1.5.5. Calculation and data presentation ………... 19
References ……….. 20
Chapter Two - Araucaria forest dynamics in relation to fire frequency in southern Brazil based on fossil and modern pollen data ……….. 26
2.1. Abstract ……….. 27
2.2. Introduction ………. 27
2.3. Environmental setting ……… 29
2.4. Material and Methods ……… 31
2.5. Results ………. 32
2.6. Interpretation and Discussion ……….. 45
2.7. Conclusion ……….. 49
2.8. References ……….. 50
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Chapter Three - Palaeoenvironmental history of the São Francisco de Paula region in
southern Brazil during the late Quaternary inferred from the Rincão das Cabritas core …………. 54
3.1. Abstract ……… 55
3.2. Introduction ………. 55
3.3. Environmental setting ……… 57
3.4. Methods ………... 60
3.5. Results ………. 60
3.6. Interpretation and Discussion ………... 67
3.7. Conclusions ………. 75
3.8. References ……….. 76
Chapter Four - New insights into vegetation, climate and fire history of southern Brazil revealed by a 40,000 years-old environmental record from the State Park Serra do Tabuleiro ………. 80
4.1. Abstract ……… 81
4.2. Introduction ………. 81
4.3. Regional setting ……….. 82
4.4. Material and Methods ……… 85
4.5. Results ………. 87
4.6. Interpretation and Discussion ……….. 97
4.7. Conclusions ………. 103
4.8. References ……….. 104
Chapter Five – Synthesis ……… 108
5.1. Late Pleistocene period ………. 109
5.1.1. Pre-Last Glacial Maximum ………..……… 109
5.1.2. Last Glacial Maximum ………. 110
5.1.3. Late Glacial ……… 111
5.2. Holocene period ………. 112
5.2.1. Early Holocene ……….. 112
5.2.2. Mid-Holocene ……….………... 113
5.2.3. Late Holocene ………... 114
5.3. Conservation ……….………. 115
5.3.1. Human impact on the grassland and forest ecosystems during the last centuries ………. 115
iii
5.3.2. Campos-Araucaria forest mosaics and its sharp borderline ………. 116
5.3.3. Impact of climate changes on forest ecosystems ……… 117
Summary ………... 119
Zusammenfassung ……….. 121
Resumo ………. 123
Appendices A. Complete list of identified pollen and spore types of the São José dos Ausentes (SdA), Rincão das Cabritas (RdC) and Ciama 2 records as well as of the surface soil samples (soil SdA) ……… 125
B. Complete list of pollen and spore types counted in the sedimentary records and soil samples grouped into different ecological groups ………... 134
C. Photo gallery: Illustration of some pollen and spores types ... 139
D. Complete pollen diagrams of the studied records ……….………. 152
E. Upper Pleistocene to Holocene Peatland Evolution in Southern Brazilian Highlands as Depicted by Radar Stratigraphy, Sedimentology and Palynology …...………... 179
iv Acknowledgements
The time writing this thesis has been hard but it was a great phase of intensive learning. I have to thank all people who contributed to and were involved in the successful completion of the thesis.
Funding was provided by Deutsche Forschungsgemeinschaft (DFG) project BE 2116/9-1.
First, I wish to thank my leading supervisor, Prof. Dr. Hermann Behling for giving me the opportunity to work in his department and for introducing me to the subject of Palynology. Further, I would like to thank my co-supervisor Prof. Dr. Erwin Bergmeier for his co-operation and help, as well as for his interest in the project. I would like to express my sincere gratitude to Sonia Fontana, Thomas Giesecke, Sander van der Kaars, Ellyn Cook, Gerald Islebe and Frank Schlütz for scientific discussions, critical comments about the work and productive collaboration while writing this thesis.
Special thanks to all members of the department, especially to Ursula Grothmann for helping me with administrative issues and Jörg Christiansen for solving computer problems. At this point, I would like to thank Nele Jantz for the taking of pollen and spore pictures and Martin Zweigert for sample preparation in the laboratory.
Nicht zuletzt möchte ich den „Villa Hexen“ (Corinna Brunschön, Barbara Hermanowski, Lisa Schüler, Isabelle Matthias und Nele Jantz) für all die Unterstützung in den schwierigen Momenten, den Motivationsnachschub und die unendliche Hilfe bei meiner Arbeit danken.
Agradeço ao meu pai por toda a ajuda em campo, como motorista e principalmente como guia. Aos meus colegas palinólogos Gisele L. de Lima, Renato B. Macedo, Rodrigo R. Cancelli, Andréia C. P. Evaldt e Prof. Soraia G. Bauermann, assim como à Renata I. Duzzioni, seu Weber e José Pedro P. Trindade pela grande ajuda durante os trabalhos de campo na Serra Geral e na Serra do Tabuleiro.
Em especial, agradeço à minha família pela força e apoio emocional, principalmente meus pais, grandes incentivadores, que sempre me encorajaram e ajudaram. Ao meu querido marido e companheiro Marius pelo carinho e paciência, bem como pela ajuda nas situações mais difíceis.
Muito obrigada!
v Preface
This PhD thesis, written as a cumulative work, has been accomplished at the Department of Palynology and Climate Dynamics at the University of Göttingen between March 2007 and December 2010. The thesis is composed of three different parts: a general introduction in Chapter 1, three independent articles presented in Chapter 2 to 4, and a synthesis in Chapter 5 integrating conclusions of the previous chapters together with a discussion. A fourth article in which the co-author Vivian Jeske-Pieruschka has written the palynological part on basis of data presented in Chapter 4 is attached in Appendix E. Tables and figures are inserted directly in the text following his statement on the text and enumerated separately for each chapter. Each article has been submitted separately for publication in international scientific journals and is arranged according to the layout of the journal.
The reference style also follows the formatting rules of the designated journal except for Chapter 1. A summary of the thesis in English, German and Portuguese is given at the end. A complete list and some illustrations of identified pollen and spore types as well as complete pollen diagrams of the studied sediment records are included in the appendices.
1
CHAPTER 1
General Introduction
2 1.1. The Atlantic Forest Biome
The mega-diverse country of Brazil encompasses six major biomes: Amazon, Cerrado, Caatinga, Atlantic Forest, Pantanal and Pampa (IBGE, 2004). The Atlantic Forest biome, considered one of the 25 global biodiversity hotspots (e.g. Myers et al., 2000; Tabarelli et al., 2005), comprises one of the most important tropical forests world-wide. It extends along the Brazilian Atlantic coast from north to south across several mountain ranges such as the Serra Geral and Serra do Tabuleiro (see 1.4.2, Fig. 5) and extends into the inland bordering Uruguay, northeastern Argentina and eastern Paraguay. The Atlantic Forest biome, situated in the most urbanized area of the country with more than 112 million inhabitants (Fundação SOS Mata Atlântica/INPE, 2009) continues to be under anthropogenic threat since European colonization around 1500 years AD (e.g. Morellato and Haddad, 2000). This biome, represented by only 7.6% of severely fragmented remaining areas (CN-RBMA, 1999), has already lost more than 90% of its original cover (Fig. 1). The Atlantic Forest biome represents therefore the most devastated vegetation of the country.
Figure 1. Map showing forest remnants of the Atlantic Forest original cover in Brazil.
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The Atlantic Forest biome is composed of different vegetation types (Fig. 2) considered as associated ecosystems and thus forming contrasting landscapes. These ecosystems vary highly depending on the altitudinal gradient and associated temperature as well as on their proximity to the ocean, rainfall regime and edaphic properties (Raedig and Lautenbach, 2009). The different vegetation types belonging to the Atlantic Forest biome include Atlantic rainforest, open ombrophylous forest, Araucaria forest, Deciduous forest, Tropical semideciduous forest, pioneer vegetation formations and highland Campos. The vegetation types studied and discussed in this thesis are independent ecosystems and correspond to the highland Campos, Araucaria forest and Atlantic rainforest. They dominate the landscape of the southern Brazilian highlands and the escarpments, and overall picture a fascinating mosaic of subtropical grassland and forest ecosystems. The Atlantic Forest biome together with the Pampa biome, specifically the forest and grassland ecosystems associated with these two biomes in southern Brazil, were identified as priority areas for conservation and of extreme biological importance due to their high level of endemism and great biodiversity (Conservation International do Brasil, 2000). Although well documented, the Campos flora of the Atlantic Forest biome with 1161 vascular plant species (107 are endemic) (Boldrini et al., 2009) still harbor undescribed species (Boldrini, 2009). Therefore, the biodiversity of southern Brazilian ecosystems is probably much greater than assumed so far.
The Campos vegetation has been used for pasture since European colonization. Since then, widespread deforestation and ecosystem alteration were the consequences of human activity in the Araucaria forests in the southern Brazilian highlands and the Atlantic rainforests on the slopes.
Concerning land-use practices and climate change in the southern region of the Atlantic Forest biome and its associated ecosystems, palaeoenvironmental studies contribute significantly towards the understanding of vegetation dynamics and climate change. Thus, palynological studies can offer palaeoenvironmental information useful for the development of conservation and management strategies for these ecosystems, which are highly vulnerable to global change.
Two study sites on the Serra do Geral were chosen for palynological and charcoal analysis due to their locality relative to surrounding vegetation, which offer a great possibility to study the origin, dynamics and stability of grassland and forest ecosystems including human activities and fire history.
In addition, the obtained information can also be compared to the results of previously accomplished palynological studies in the same region. The third study site on the Serra do Tabuleiro was chosen because of its special geographical position, namely the proximity to the coast and its isolation from other mountain ranges. That offers an excellent opportunity two study the development and history of Atlantic rainforest and Araucaria forest as well as fire events during the past.
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Figure 2. Different vegetation types of the Mata Atlântica Domain.
(source: Digitalização do Mapa de Vegetação do Brasil, FIBGE, 1993, escala 1:5:000.000 – Instituto Socioambiental/Fundação SOS Mata Atlântica) slighly modified. The circle on the map indicates the studied region.
(www.rbma.org.br/anuario/mata_02_eco__ssistema.asp)
1.2. Previous studies on the ecosystems of the Atlantic Forest Biome in southern Brazil during the late Quaternary
During the last few years, palaeoenvironmental studies of the Atlantic Forest biome were carried out for the southeastern (e.g. Behling and Lichte, 1997; Behling, 1998, 2002; Ybert et al., 2003; Garcia et al., 2004; Behling and Safford, 2010) and southern region of Brazil (e.g. Behling et al., 1997; Behling and Negrelle, 2001; Lorscheitter, 2003; Cruz Jr. et al., 2005, 2006; Leal and Lorscheitter, 2007; Oliveira et al., 2008 a,b; Leonhardt and Lorscheitter, 2010). Nevertheless, studies on development and dynamics of the Atlantic rainforest ecosystem reaching into the full Glacial period still lack for southern Brazil. For the Santa Catarina lowlands, Behling and Negrelle (2001) documented initial Atlantic rainforest development after 12,300 yr BP (uncalibrated years before the
5
present) as part of a successional sequence and the appearance of a dense forest only after the marine regression at about 6100 yr BP. For Rio Grande do Sul, Lorscheitter (2003) indicated fossil evidence of some disperse Atlantic rainforest taxa at the beginning of the Holocene at about 10,000 – 8000 yr BP along the coastal plain and valleys. More recently, Leal and Lorscheitter (2007) propose a migration of Atlantic rainforest species from east to west on the lower slope of the Serra Geral, Rio Grande do Sul since 8800 yr BP.
For the southern Brazilian highlands Campos vegetation seems to be the predominant vegetation type during glacial times. The hypothesis of some authors about Campos vegetation as a relict from drier climatic conditions in the past (Rambo, 1956, 1994; Klein, 1960, 1975) has been confirmed by palynological studies in the last decades (Roth and Lorscheitter, 1993; Behling, 1995, 1997, 1998, 2002; Behling et al., 2001, 2004; Leonhardt and Lorscheitter, 2010). Studies of late Quaternary palaeoenvironments in southern Brazilian grasslands, suggest initial Araucaria forest expansion after 2000 yr BP in Serra do Araçatuba (Behling, 2007) and about 2850 yr BP in Serra dos Campos Gerais (Behling, 1997), both in Paraná state. For the highlands of Santa Catarina state, Behling (1995) proposed first Araucaria forest expansion at about 3460 yr BP in Serra da Boa Vista and at about 2390 yr BP in Serra do Rio do Rastro. In Rio Grande do Sul, located further south of Santa Catarina, initial Araucaria forest expansion is documented for about 3950 yr BP in Cambará do Sul (Behling et al., 2004) and after 4000 yr BP in São Francisco de Paula region (Leonhard and Lorscheitter, 2010). Marked Araucaria forest expansion is reported for about 1400 cal yr BP (calibrated years before the present) in Paraná state (Behling, 1997, 2007) and since the last 1000 years for the highlands of Santa Catarina and Rio Grande do Sul sates (Behling, 1995; Behling et al., 2001; Behling et al., 2004; Behling and Pillar, 2007). Although the early expansion of Araucaria forests occurred at different times, all interpretations suggest Araucaria forest initial expansion through migration from gallery forests along rivers and wet areas after mid-Holocene.
1.3. Aims of the work
At present, the remaining areas of Campos on the highlands represent remnants of early and widely expanded vegetation of glacial times that was gradually replaced by forest ecosystems during the late Holocene (see 1.2). However, on the highlands are also Campos areas of anthropogenic origin which resulted from the introduction of cattle after successive logging and burning. Despite a subtropical humid climate, which favors grassland replacement by forest (e.g. Lindman, 1906; Rambo, 1951; Klein, 1975), natural patches of grassland exist within the forest area (e.g. Klein, 1960; Hueck, 1966; Oliveira and Pillar, 2004). Still unclear and controversial is the reason of sharp borderlines which can be observed between forest and grassland (Fig. 3a). According to some authors, the natural
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vegetation of Campos-Araucaria forest mosaics covering the highlands in southern Brazil and the marked borderline should be determined by grazing and fire regimes (e.g. Pillar and Quadros, 1997;
Pillar, 2003; Overbeck et al., 2007). For some regions on the southern Brazilian highlands, where regional economies are based on land use such as cattle farming and agricultural activities (Fig. 3b) together with silvicultural production (extensive Pinus plantations), a better understanding of past environmental changes is of crucial importance for predicting climatic and vegetational changes.
Therefore, human activities and their possible role in the formation of Campos-Araucaria forest mosaics also need to be explored by mean of pollen and charcoal analysis.
Figure 3a shows an example for sharp borderline between Campos and Araucaria forest while figure 3b illustrates different forms of land use with Pinus sp. plantation back and in front rural agriculture.
The main goals of the present study are:
a) To reconstruct vegetation development and dynamics, fire history and climate changes for the southeastern highlands of Rio Grande do Sul state and for the isolated Serra do Tabuleiro, Santa Catarina state during the late Quaternary;
b) To investigate the origin, development and dynamics of the Campos-Araucaria forest mosaics ecosystems on the southern Brazilian highlands;
c) To investigate the development and history of the Atlantic rainforest;
d) To elucidate forest expansion in different time periods;
e) To clarify if the present grasslands are natural or of anthropogenic origin and if the existence of isolated Araucaria forests originates from refugia of the last glacial period in the Serra do Tabuleiro coastal mountain range;
f) To understand how the frequently observed sharp borderlines between Campos and Araucaria forest have been formed and how they are maintained;
g) To examine and interpret the factors controlling the dynamic and stability of Campos- Araucaria forest mosaics;
a b
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h) To discover since when and how strong grassland and forest ecosystems have been affected by human activities;
i) To use this background information as important contribution for sustainable conservation and management of the species rich vegetation in southern Brazil;
j) To connect these palaeoenvironmental studies with two other international research projects;
k) To compare the results with other localities;
With the purpose of approaching these research questions, two sediment archives from the Serra Geral and one from the Serra do Tabuleiro have been studied by means of pollen and charcoal analysis. These sediment records were cored from bogs situated in the “Mata Atlântica” region.
Therefore, these studies provide a basis to understand the development, stability and dynamics of modern ecosystems, including their biodiversity in space and time.
This study provides interpretations on palaeoecological changes and anthropogenic activities throughout the late Quaternary that could be integrated into two research projects. Part of this thesis (Chapter 2 and 3) is related to a research project titled „From Landscape to Ecosystem: Across-scales Functioning in changing environments (LEAF)” financed by the InterAmerican Institute for Global Change Research (IAI).
A smaller cooperation between the Department of Geosciences at the Universidade Federal de Santa Catarina, Brazil and the Department of Palynology and Climate Dynamics at the University of Göttingen about palaeoenvironmental characterization of the highlands of the Serra do Tabuleiro was funded by FAPESC – Fundação de Apoio à Pesquisa Científica e Tecnológica do Estado de Santa Catarina and resulted in two articles submitted to international journals (Chapter 4 and Appendix E).
1.4. Study region
1.4.1. Location of the study sites
The research was performed at three study sites in the southern Brazilian highlands, as shown by figure 4. The southern region of Brazil, covering 577.214 km², corresponds to the smallest of the five regions of Brazil and encompasses the states of Paraná, Santa Catarina and Rio Grande do Sul.
It borders Uruguay, Argentina and Paraguay to the west, the Central-West region and the Southeast region of Brazil to the North and the Atlantic Ocean to the east. The highlands of Rio Grande do Sul (Serra Geral) are located in the northeastern part of this state while the isolated Serra do Tabuleiro lies in the east of Santa Catarina state (Fig. 5).
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Figure 4. Location of southern Brazil with indication of the study sites of this work: Ciama 2 (Ciama), São José dos Ausentes (SdA) and Rincão das Cabritas (RdC).
The first study area São José dos Ausentes (SdA) (50°02´39.9´´W, 28°56´16´´S at 1050 m a.s.l.) is situated between the village of Cambará do Sul and São José dos Ausentes. The second one, Rincão das Cabritas (RdC) (50°34´22´´W, 29°28´35´´S at 895 m a.s.l.), is situated in a rural area of São Francisco de Paula municipality. Both sites are located in the Serra Geral formation situated in the northeastern highlands of Rio Grande do Sul state. The escarpments of the Serra Geral mountain range, in the part of Rio Grande do Sul state, are situated at a distance of approximately 25 km from the coast (Itaimbezinho Canyon) and reaches an average elevation of 950 meters.
The third study site lies in the Ciama region (48°52´5.33´´W, 27°53´48.46´´S, at 860 m a.s.l.), on the highlands of the Serra do Tabuleiro, Santa Catarina state. The Serra do Tabuleiro is an isolated coastal mountain range reaching elevations up to 1260 m and is inserted into the State Park Serra do Tabuleiro. The Park was founded in 1975 and includes 9 municipalities close to the capital city of Florianópolis. With an area of 87.405 ha, it covers approximately 1% of the Santa Catarina state in southern Brazil, being the largest conservation unit in this State (Oliveira et al., 2006).
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Figure 5. Topographical map of Brazil (after Menegáz, 2006) showing the southern Brazilian highlands: Serra Geral and Serra do Tabuleiro (slightly modified).
1.4.2. Geomorphology and soil
The southernmost highlands of southern Brazil, on the northeastern part of Rio Grande do Sul state, the so-called Serra Geral formation corresponds, in geomorphological terms to a plateau (Planalto Meridional). This geomorphological unit is formed by layers of basalt covering Jurassic/Cretaceous sedimentary rocks, the Botucatu formation. It is composed of base-rich basalt in the lower layers and acidic rocks mostly rhyolite and rhyodacite in the upper layers (IBGE, 1986).
Soil formation is affected by high precipitation rates under subtropical humid climate.
According to the Soil Map of Brazil composed by the IBGE (Brazilian Institute of Geography and Statistics) and the EMBRAPA (Brazilian Agricultural Research Cooperation), humic cambisol and leptosols occur in the highlands (http://mapas.ibge.gov.br/solos/viewer.htm). A recent study on soils in
10
the Pró-Mata area, southern Brazilian highlands (Dümig, 2008), concludes that soils in grasslands of the region are more correctly termed andosols while umbrisols develops in the Araucaria forest.
The isolated mountain range of Serra do Tabuleiro is predominantly composed by granite intrusive rocks (Égas et al., 2005) of approximately 516 ± 12 Ma (Basei, 1985 in Tomazzoli et al., 2005). Soils of the Serra do Tabuleiro are identified as cambisols and acrisols or lixisols (http://mapas.ibge.gov.br/solos/viewer.htm).
1.4.3. Climate
The climate of southern Brazil is influenced by the South Atlantic Anticyclone transporting equatorial warm and humid air masses from the tropical Atlantic Ocean over the continent during the whole year. This influence is weaker during the austral winter (June-August) and more frequent during the summer (December-February). Another atmospheric circulation also influences the climate of the southern Brazil mostly during the winter, the Polar Anticyclone with dry and cold air masses. These air masses formed in the Antarctic and its trajectory over the South-American continent provoke strong rainfall when it clashes with tropical warm and humid air masses (Nimer, 1989). The rainfall is also intensified by the elevation of air masses promoted by the relief that cause rain after their cooling and condensation. The amount of moisture depends on the proximity to the Atlantic Ocean and in consequence, precipitation reduces from the coast to inland (east-west).
The climate on the highlands of Rio Grande do Sul is subtropical humid, with high rainfall rates (up to ca. 2500 mm/year) distributed throughout the year without a pronounced dry period (Moreno, 1961). It is classified as wet mesothermic climate (Cfb, Köppen) and characterized by temperatures lower than 22°C in the warmest month and higher than 3°C in the coldest month. The winters are cold, with temperatures below 0 °C in cold winter nights and rare occurrence of snow at higher elevations;
frosts are frequent. For the Santa Catarina highlands, the climate is also characterized as mesothermic Cfb (above 800 m a.s.l., Köppen) with high mean annual precipitation ranging from 1600 to 1800 mm/year, relatively uniformly distributed throughout the year.
Precipitation anomalies are associated with El Niño Southern Oscillation (ENSO) and La Niña events. Excessive rainfall events are related to El Niño whereas La Niña reduces rainfall in southern Brazil (Grimm et al., 1998, 2000). Interannual variability of rainfall is also related to anomalies in sea surface temperature (SST), with increased (decreased) precipitation associated with warm (cold) deviation of SST in the southwestern Atlantic Ocean (Díaz et al., 1998; Barros et al., 2000).
11 1.4.4. Current distribution of the vegetation
At present, a fascinating landscape formed by grassland-forest mosaics constitutes the highlands of southern Brazil (Fig. 6). These mosaics formed by large areas of subtropical grassland, so-called Campos, intercepted by patches of Araucaria forest, characterize the picture across the southern Brazilian highlands representing thus the landscape of the region (e.g. Klein, 1960; Rambo, 1994). Although Araucaria forest is the main vegetation type on the highlands forming Campos-forest mosaics, an exuberant forest ecosystem, the Atlantic rainforest, can be seen growing on the slopes of the coastal mountain ranges (Fig. 7).
Figure 6. Mosaics of Campos-Araucaria-forest in the Serra Geral (a) and in the Serra do Tabuleiro (b).
Figure 7. Atlantic rainforest on the slopes of the coastal mountain range of Serra Geral (a) and of Serra do Tabuleiro (b).
The Campos ecosystem in the highlands of Rio Grande do Sul state is mainly composed of the plant families Poaceae, Asteraceae, Fabaceae, Cyperaceae and Apiaceae (Boldrini, 2009).
Among the dominant Poaceae species, Boldrini (1997) identified Andropogon lateralis, Axonopus siccus, Paspalum maculosum, Schizachyrium tenerum and S. spicatum for well-drained and Andropogonmacrothrix and Paspalum pumilum for poorly drained grasslands.
Araucaria angustifolia (Araucariaceae) is the most physiognomically important tree species of the Araucaria forest ecosystem on these highlands. The geographical distribution of Araucaria
a b
a b
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angustifolia is in the southern states of Brazil that are Rio Grande do Sul, Santa Catarina and Paraná.
The species also occurs isolated or in small populations in São Paulo, Rio de Janeiro and Minas Gerais state at higher elevations (Hueck, 1953)(Fig. 8). The Araucaria forest consists of species such as Podocarpus lambertii (Podocarpaceae), Drimys spp.(Winteraceae), Mimosa scabrella (Fabaceae), Ocotea pulchella, O. puberula, Nectandra spp. (Lauraceae), Ilex paraguariensis, Ilex spp.
(Aquifoliaceae), Matayba elaeagnoides, Cupania vernalis (Sapindaceae) and various species of the Myrtaceae family (Reitz et al., 1988). The slopes of the Serra Geral (Rio Grande do Sul state) are covered by Atlantic rainforest from the lower altitudes up to higher elevations where a gradual transition between the Araucaria forest and the Atlantic rainforest can be observed (Fig. 9).
The species-rich Atlantic rainforest is composed of numerous tree species with a predominance of Lauraceae (eg. Ocotea spp., Nectandra spp.) and Myrtaceae (eg. Myrcia spp., Myrceugenia spp., Calyptranthes spp., Gomidesia spp.). Other representative taxa are: Alchornea spp. (Euphorbiaceae), Clethra scabra (Clethraceae), Weinmannia spp. (Cunoniaceae), Inga spp.
(Fabaceae), Cedrela spp., Cabralea canjerana (Meliaceae) as well as Mimosaceae (Piptadenia, Parapiptadenia, Anadenanthera). However, numerous lianas and epiphytes belonging to Bromeliaceae, Orchidaceae, Araceae, Cactaceae as well as pteridophytes are characteristic for the Atlantic rainforest ecosystem. A more extensive description of the Campos and forests of southern Brazil was published by Lindman (1906). The southern Brazilian vegetation has also been described in Rambo (1951, 1956), Klein (1960, 1975) and Hueck (1966). The two study sites on the Serra Geral, Rio Grande do Sul state, were covered by mosaics of natural Campos and Araucaria forest prior to the arrival of European settlers.
Figure 8. Original distribution of the Araucaria-forest in Brazil
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Figure 9. Vegetational transition between two forest types: Araucaria forest and Atlantic rainforest on the upper slopes of the Serra Geral.
The present vegetation of the Serra do Tabuleiro in Santa Catarina state is composed of Atlantic rainforest on the slopes, Araucaria forest at higher elevations and Campos ecosystems at upper altitudes. This isolated coastal mountain range is inserted into the State Park Serra do Tabuleiro, which can be differentiated into five phytogeografic regions (Klein, 1981). In the eastern part, on the Quaternary sandy plain, coastal vegetation (so-called restinga) and mangroves occur.
Atlantic rainforest is the dominating vegetation type in the Park, covering the lowland and the slopes.
Araucaria forest and Campos occur at higher elevations. A comprehensive description of the recent vegetation of the park is given by Klein (1978, 1981).
1.5. Methods 1.5.1. Fieldwork
Two fieldwork periods during the time of 23.06.2007 until 04.07.2007 and from 06.11.2008 to 11.11.2008 were carried out on the highlands of Rio Grande do Sul and Santa Catarina state. During the first fieldwork period, one sedimentological record from a peat bog located on the northeastern highlands of Rio Grande do Sul was collected. Additionally, 18 surface soil samples were taken across a transect in an area covered by Campos and Araucaria forest in order to study the modern pollen rain in a grassland-forest-mosaic landscape. Furthermore, 20 pollen traps were installed in the Pró-Mata research area that also lies on the Rio Grande do Sul highlands. For the Santa Catarina highlands, 15 pollen traps were installed in the Serra do Tabuleiro. The peat record was sampled using a Russian corer. Each 50 cm long core section was sealed with split PVC tubes and wrapped with plastic film
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before stored in a dark and cold room (~4°C) until opened for sediment description and subsampling.
The peat sediment and the transects of installed pollen traps as well as the collected surface soil samples are listed in Table 1.
Table 1. Collected samples and installed pollen traps during fieldwork.
Sample type Sampling/installing date
Location Elevation
(m a.s.l.)
Coordinates (GPS)
Rincão das Cabritas (RdC) peat core
23.06.2007 São Francisco de Paula- Serra Geral
894 29°28.591`S 50°34.370`W
Surface soil samples (transect of 18 sites)
25.06.2007 São José dos Ausentes – Serra Geral
1053 - 1098
28°56`18.3``S 50°02`38.2``W to 28°56`09.3``S 50°02`26.7``W
Pollen traps (transect of 4 sites)
30.06.2007 Ciama –Serra do Tabuleiro
873 - 877
27°54´01,2´´S 48°52´10.9´´W to 27°54´00.1´´S 48°52´10.1´´W
Pollen traps (transect of 11 sites)
01.07.2007 Clino – Serra do Tabuleiro
1148 - 1186
27°49´13´´S 48°53´28.8´´W to 27°49´12.1´´S 48°53´24.7´´W
Pollen traps (transect of 20 sites)
03.07.2007 Pró-Mata – Serra Geral 900 - 935
29°29`16.2``S 50°13`0.1``W to 29°29`12.2``S 50°13´22.1``W
1.5.2. Analyzed sediment cores
The São José dos Ausentes (SdA) core has a length of 120 cm and was taken from a peat bog of ca. 30 m of diameter located at the border of a disturbed Araucaria forest island, surrounded by Campos (Fig. 10). It was collected by Hermann Behling and Soraia Girardi Bauermann on November 13th 2004 during fieldwork in southern Brazil. This peat core has an extrapolated age of 590 cal yr BP at 98 cm core depth. Furthermore, 18 surface soil samples were taken across a 340 m long transect (Fig. 11) in the research area of the peat core close to the village of São José dos Ausentes with the intention of studying the modern pollen rain of Campos-Araucaria forest ecosystems.
15
Figure 10. Cored peat bog situated between the village of Cambará do Sul and São José dos Ausentes on the Serra Geral, Rio Grande do Sul state. The studied peat at right side of the picture is bordered by a small, disturbed Araucaria forest island surrounded by Campos.
Figure 11. Surface soil transect in the same area of the sedimentary record to estimate the modern pollen rain of the two local vegetation types, Campos and Araucaria forest in order to holistically interpret the palaeodata from this locality.
16
The Rincão das Cabritas (RdC) core, reaching 281 cm length, was collected on June 23rd 2007 from a ca. 5000 m2 bog situated within an Araucaria forest (Fig. 12). The base of the core is extrapolated to 16,700 cal yr BP.
Figure 12. Sampled peat within the rural property Rincão das Cabritas located on the Serra Geral, Rio Grande do Sul state.
The Ciama 2 core with a length of 169 cm was taken from a peat bog located in the Campos surrounded by Atlantic rainforest and Araucaria forest (Fig.12). Marcelo Accioly Teixeira de Oliveira and Hermann Behling took this sediment core during fieldwork on August 13th 2005. The extrapolated basal age at 168 cm core depth is 39,720 yr BP.
Figure 13. Peat bog cored by the Ciama area in the Serra do Tabuleiro, Santa Catarina state.
17 1.5.3. Laboratory techniques
Preceding sample preparation for pollen analysis, the lithology of each sediment core was described. Subsequently, subsamples were taken for pollen, charcoal and radiocarbon analysis. For the SdA sedimentary record, a total of 75 samples of 0.25-1 cm3 were used for pollen and charcoal analysis. Samples were taken at 1 cm intervals between 0-32 cm, and every 2 cm between 33-120 cm core depth. For the RdC peat core, a total of 71 samples (0.25 -1 cm3) were taken at 4 cm intervals. At last, 83 volumetric subsamples (0.25 cm3) were taken every 2 cm along the Ciama 2 core, except between 0-8 cm core depth, i.e. 2 samples with interval of 4 cm. Differences in sampling intervals along each core are a result of different core lengths and depend on the sedimentation time that they encompass. The same analytical standard methods were applied for the surface soil samples (ca. 2 cm depth of soil and litter) as for the fossil pollen.
All samples were processed and prepared for pollen and charcoal analysis in the palynological laboratory with standard pollen analytical methods after Faegri and Iverson (1989). Prior to pollen preparation, samples were treated with hydrofluoric acid (HF) to digest siliceous matter as clay (sometimes containing layers of fine sand). One tablet of Lycopodium clavatum marker was added to each sample for determination of pollen and charcoal concentration (grains/cm3; particles/cm3) and accumulation rates (grains/cm2/year; particles/ cm2/year) (Stockmarr, 1971). Hydrochloric acid (HCl) was used to dissolve the carbonate present in the Lycopodium tablets. Subsequently, the samples were washed though nested metal screens with mesh size of 150 μm. Preceding acetolysis, which is applied for cleaning and to dye pollen, spores and palynomorphs, the samples were dehydrated with acetic acid (CH3COOH). Finally, the pollen residues were mounted in glycerin gelatin and searched for pollen grains under a light optical microscope and counted up to a minimum of 300 pollen grains at each level. Charcoal analysis is based on microscopic (5 – 150 µm) charred particles which were counted on the pollen-slides.
In total, 18 subsamples were taken from the cores and sent to radiocarbon dating through Accelerator Mass Spectrometry (AMS) at the Institute of Physics of the Erlangen-Nürnberg University, Germany. The resulting ages were converted into calibrated calendar years before present (cal yr BP) with CalPal (Weninger et al., 2004) or using the software CALIB 6.0 (Stuiver and Reimer, 1993) applying the data set of SHCal04 (McCormac et al., 2004) and of intcal09.14c (Reimer et al., 2009). A chronological control is given for each sediment core through the radiocarbon ages that were used for constructing the age-depth models for the cores assuming an equal sedimentation rate. Table 2 shows radiocarbon dates for the São José dos Ausentes (SdA), for the Rincão das Cabritas (RdC) and for the Ciama 2 sediment archives.
18
Table 2. Radiocarbon dates from the studied sedimentary profiles.
Core name Laboratory
code
Sample depth (cm)
Sample type
Conventional age (14C yr BP)
Calendar age (cal yr BP)
São José dos Ausentes (SdA) Erl-11259 14 peat -1424±37 0
São José dos Ausentes (SdA) Erl-11260 26-30 wood 277±36 364±58
São José dos Ausentes (SdA) Erl-11261 71 wood 451±37 507±18
Ricão das Cabritas (RdC) Erl-12100 45 wood 704±42 612
Ricão das Cabritas (RdC) Erl-15120 85 wood 1786±38 1641
Ricão das Cabritas (RdC) Erl-11387 126 peat 2847±37 2892
Ricão das Cabritas (RdC) Erl-12101 171 peat 5997±45 6769
Ricão das Cabritas (RdC) Erl-12655 210 peat 10245±68 11877
Ricão das Cabritas (RdC) Erl-12102 228 peat 12578±66 14806
Ricão das Cabritas (RdC) Erl-11388 279 wood 13503±68 16679
Ciama 2 Erl-11255 34 peat 459±44 478
Ciama 2 Erl-12097 47 peat 3820±39 4129
Ciama 2 Erl-12656 61 peat 7327±45 8092
Ciama 2 Erl-11256 71 peat 10536±63 12545
Ciama 2 Erl-12657 83 peat 13399±72 15916
Ciama 2 Erl-12098 94 peat 19439±115 23126
Ciama 2 Erl-12099 122 peat 25380±152 -
Ciama 2 Erl-11257 167 peat 39407±681 -
1.5.4. Identification of pollen and spores
Although pollen preservation and its accumulation can vary markedly depending on the sampled material, almost all counted levels had satisfactory or good pollen preservation and yielded sufficient pollen quantity to be counted. This was the case for the pollen amounts in the complete Rincão das Cabritas and Ciama 2 core as well as for the modern pollen rain in the surface soil samples. Samples below 58 cm core depth in the São José dos Ausentes core yielded low pollen quantities and had bad pollen preservation and were often sterile below 98 cm core depth and could not be counted. Pollen and spores were identified at magnifications of 400 and 1000 x, and counts reach to about 300 pollen grains of terrestrial flowering plants per sample. The identification of the diverse pollen and spore types was simplified by the use of the reference collection of the Department of Palynology and Climate Dynamics, University of Göttingen, together with morphological descriptions by Behling (1993) and Cancelli (2008). Occasionally, a precise identification was not possible. In this case, the word “type” was adopted referring to the most likely taxa. Pollen types that could not be identified were classified by morphological characteristics and included into the “Unknowns” group.
19
The number of identified pollen and spore taxa as well as the number of counted subsamples for each sedimentary record and surface soil samples is listed in Table 3.
Table 3. Number of identified pollen and spore types as well as number of counted subsamples for each sediment record. Total number indicates the sum of different identified pollen and spore found in all samples (see Appendix A).
Core name Number of identified pollen taxa
Number of identified spore taxa
Number of counted sub-samples
São José dos Ausentes 170 16 43
Rincão das Cabritas 114 15 71
Ciama 2 155 16 83
Transect soil samples at São José dos Ausentes
82 10 18
Total 241 49 215
1.5.5. Calculation and data presentation
Pollen and spore data were used with the purpose of reconstructing past vegetation in the highlands of Rio Grande do Sul (Serra Geral) and of Santa Catarina (Serra do Tabuleiro). All identified pollen and spore types were grouped into different ecological groups (Campos, Araucaria forest, Atlantic rainforest, Aquatics, Tree ferns, Pteridophyta and Mosses). Pollen taxa that could not be included in any other vegetation type or have wider geographical distributions, were assigned to
“Others”. The classification of the pollen and spores in the respective vegetation types was based on the recent vegetation present in each study area (Appendix B). Pollen and spores were calculated as percentages of the pollen sum, which includes all different pollen types of grasses, herbs, shrubs and trees. Spores of pteridophyte and mosses as well as pollen grains of aquatic taxa were excluded from the total pollen sum. Fire event reconstructions are based on microscopic (5 – 150 µm) charred particles and are presented as concentration and influx rates in the pollen diagrams. Results of pollen and spore analysis together with charcoal data are presented as pollen diagrams in percentages of the total pollen sum, calculated and plotted using the software TILIA and TILIAGRAPH (Grimm, 1991).
The zonation of the pollen records is based on marked changes in the pollen assemblages i.e.
changes of the most important taxa and/or changes in the pollen composition reflecting vegetational changes. Zonation was also based on the cluster dendrogram calculated with CONISS (Grimm, 1987).
20 References
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26
CHAPTER 2
Araucaria forest dynamics in relation to fire frequency in southern Brazil based on fossil and modern pollen data
Vivian Jeske-Pieruschka, Alessandra Fidelis, Rodrigo S. Bergamin, Eduardo Vélez and Hermann Behling
Review of Palaeobotany and Palynology 160 (2010): 53-65
27 Abstract
To elucidate the relationship between forest dynamics and fire frequency, pollen percentages and charcoal amounts from a 120 cm long peat core and from samples of modern pollen rain were collected along a transect. The study site in southern Brazil is characterized by a species-rich mosaic of grassland-Araucaria forest. It is of crucial importance for management strategies for conservation to understand the development and maintenance of these vegetation mosaics including their sharp forest-grassland boundaries. During the late Holocene, considerable changes occurred in the area.
From Anno Domini (AD) 1360 to 1410, the area was dominated by Campos (grassland) vegetation and fire was very common. From AD 1410 to 1500, Araucaria forest expanded and fire was less frequent. From AD 1500 to 1580, Campos grassland spread and the Araucaria forest ceased its development, apparently due to the increase of fire. From AD 1580 to 1935, after a decrease in fire frequency, Araucaria forest expanded again. From AD 1935 to the present, the Araucaria forest expanded while the Campos area decreased. Fire was very rare in this period. The results indicate a strong interaction of forest expansion, forming a mosaic of Campos and Araucaria forest, and the frequency of fire during the past 600 years. A possible collapse of the indigenous population following the post-Columbian colonization in southern Brazil after about AD 1550 may have caused a great reduction of fire frequency. The introduction of cattle (probably after AD 1780) and the resulting decrease of fire frequency might be the reason for forest expansion. Fire is probably the most important factor controlling the dynamics of the forest-grassland mosaics and the formation of sharp borders between these two vegetation types.
Keywords: Late Holocene, Araucaria forest, Campos-grassland, Fire, Human impact, Pollen analysis
1. Introduction
Nowadays, the southern highland region of Brazil is covered by a mosaic of grassland-forest vegetation, which is considered part of the Atlantic Forest Biome (IBGE, 2004). This peculiar vegetational formation is basically shaped by a mosaic of grassland, so-called Campos, and Araucaria forest with its distinct sharp boundary. Pillar and Quadros (1997) and Pillar (2003) affirmed that the natural vegetation mosaic of Campos-Araucaria forest in southern Brazil, including its boundaries, might be determined by grazing and fire regimes. Thus, palaeoenvironmental studies are important tools for confirming such affirmation. Knowledge of early fire activity is relatively well documented for the southern Brazil highlands where present day vegetation is still a mosaic of Campos and forest (Behling, 1997; Behling et al. 2007). The charcoal record from the last 42,840 yr BP documents that
28
natural grassland fires were rare during the glacial periods. Frequent fires during the mid Holocene, as well as the expansion of Araucaria forests together with lower fire frequencies during the late Holocene are good indicators of anthropogenic fire (Behling et al., 2004). The reduction of fire after 500 yr BP in the tropical Americas is synchronous with the indigenous population collapse following European conquest (Nevle and Bird, 2008). The landscape of grassland-forest mosaic in the southern Brazil uplands has been under human influence, first by pre-Columbian cultures using slash and burn activity. After the 19th century, European settlers caused deforestation due to intense colonization.
According to Behling (1993, 1995, 1998, 2002) Campos covered extensive areas on the highlands of southern Brazil during the last glacial until mid Holocene times, when Araucaria forest began to expand through migration from gallery forests along rivers and wetlands since ca. 3210 cal yr BP. A pronounced expansion of the Araucaria forest is reported for about 1400 cal yr BP in Paraná state (Behling, 1997, 2007) and for about 1000 cal yr BP in Santa Catarina state (Behling, 1995). In Rio Grande do Sul state, the initial expansion occurred about 4320 yr BP, being more pronounced since 1100 cal yr BP (Cambará do Sul record, Behling et al., 2004; Behling and Pillar, 2007).
However, the history of the origin and dynamics of the Araucaria forest and Campos mosaic ecosystems is still not completely understood. Despite the very humid climate of present times, which favors replacement of grassland by forest, natural patches of grassland still exist within the forest area (Oliveira and Pillar, 2004; Overbeck et al., 2007). The reason for the sharp boundaries observed between the forest and grassland is also unclear. Therefore, past human activities and their possible role in the formation of Campos-Araucaria forest mosaics can be explored by applying both pollen and charcoal analyses.
Studies of late Quaternary palaeoenvironments of southern Brazilian highlands using palynological analysis have been published during the last few years (Behling and Pillar, 2007;
Behling et al., 2001, 2004). However, studies using modern pollen rain data to help interpret fossil pollen records are lacking for the region. Surface soil samples collected along a transect through Campos vegetation and Araucaria forest can provide useful information on the interpretation of fossil pollen records from the same locality. Thus, changes in present and past vegetation are reflected in the pollen spectra. A floristic inventory can help to interpret pollen content in surface soil samples of the local area, which can indicate the presence of taxa in the area, or even their arrival from other areas. Surface sample data combined with core analysis are useful for interpreting modern vegetation in detail (Wright, 1967). Some authors have used modern pollen spectra to assist the interpretation of fossil pollen records e.g. in the Pampa grassland in Argentina (Stutz and Prieto, 2003), in Colombian Amazonas (Berrío et al.,2003) and in neotropical ecosystems of Bolivia (Gosling et al., 2009). Behling et al. (1997) investigated modern pollen rain in the lowlands of southern Brazil to determine the pollen spectra of the local vegetation (Atlantic rain forest). Behling et al. (2001) used modern pollen from
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surface samples from São Francisco de Paula region, but they analyzed only 8 surface samples without any floristic inventory. Consequently, the necessity of studies including fossil pollen records and modern pollen combined with floristic inventories for the southern Brazil Campos is highlighted.
The aim of this study is to describe the origin and dynamics of the Araucaria forest during the early Holocene until present using palynological methods. This study also intends to investigate the relationship between fire frequency and forest expansion. Another significant aspect is to understand how the sharp borders between Campos and forest arise and which factors control and maintain them.
Knowledge about the development and maintenance of these mosaics is essential for conservation management of these species-rich ecosystems of the Atlantic rain forest.
2. Environmental setting 2.1. Study area and climate
The study area is situated in the northeastern highlands of the southernmost state of Brazil, Rio Grande do Sul (28°56`16``, 50°02`39.9``W) at a distance of approximately 9 km from the escarpment of the Serra Geral mountains range (Fig. 1). In geomorphological terms, it corresponds to the “Planalto Meridional”. The studied peat bog is at 1050 m a.s.l., with a diameter of ca. 30 m at the border of a disturbed Araucaria forest island, surrounded by Campos. The special position of the bog in relation to these vegetation types offers an excellent opportunity to investigate the origin, dynamics and stability of this Araucaria forest, island including human activities.
The climate on the highlands of Rio Grande do Sul is classified by Moreno (1961) as subtropical humid (Cfb, Köppen). It is characterized by rainfall distributed throughout the year and temperatures lower than 22°C in the warmest month and higher than 3°C in the coldest month. The South Atlantic Anticyclone and the Polar Anticyclone with its origin in the Antarctic and its trajectory over the South-American continent, dominate the atmospheric circulation over southern Brazil (Nimer, 1989). Climate records from São Francisco de Paula, approximately 76 km south of the research area, show a rainfall of ca. 2500 mm/year with a January mean temperature of 18.3°C and July mean temperature of 9.9°C; frost is common and fog occurs on average 92 days/year (Moreno, 1961).
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Figure 1. Map showing the Campos on the southern Brazil and the locality of the study area on the highlands of Rio Grande do Sul state.
Figure 2. View of the studied area with the location of modern pollen surface sample sites P1 to P18 along the transect and the analyzed peat bog.
31 2.2. Modern vegetation
The species-rich Campos is the predominant vegetation type surrounded by islands of Araucaria forest. These forest patches are composed of species associated to Araucaria angustifolia, the dominant species: Ocotea pulchella, O. puberula, Nectandra lanceolata, N. grandiflora and N.
megapotamica and diverse Myrtaceae like Myrcia bombycina, Calyptranthes concinna, Myrceugenia euosma, Gomidesia sellowiana, Psidium cattleyanum, among others. Other dominant species are:
Aquifoliaceae such as Ilex paraguariensis and Ilex spp., Sapindaceae such as Matayba elaeagnoides and Cupania vernalis and other species such as Drimys brasiliensis, Podocarpus lambertii and Mimosa scabrella (Reitz et al., 1988). The Araucaria forest vegetation is comparable to the Podocarpo lambertii-Araucarietum angustifoliae vegetation community described by Eskuche (2007). Boldrini (1997) identified Andropogon lateralis (Poaceae) as the dominant grassland species for the Campos in this region. However, Schizachyrium tenerum, Paspalum plicatulum and Axonopus siccus (all Poaceae) are also frequently found. Other grass species growing in this area are Axonopus compressus, Bromus auleticus and B. brachyanthera, forming a mosaic of C3 and C4 grasses. The Campos grasslands are also rich in Asteraceae, Cyperaceae and Leguminosae. Human induced fire is a common disturbance, and is responsible for changes in species composition.
3. Material and Methods
3.1. Sediment core and pollen analysis
The investigated core was sampled with a 50 cm long Russian corer and had a length of 120 cm. Each core section was wrapped in plastic film and stored under +4°C in dark conditions until analysis. Three subsamples of 2-3 g were used for radiocarbon dating by Accelerator Mass Spectrometry (AMS) at the laboratory of the University Erlangen-Nürnberg, Germany. A total of 75 volumetric samples of 0.25-1 cm3 were used for pollen analysis. Samples were taken at 1 cm intervals: between 0-32 cm depth, and every 2 cm between 33-120 cm depth. They were prepared with standard pollen analytical methods applying hydrofluoric acid (HF) treatment and acetolysis (Faegri and Inversen, 1989). One tablet of Lycopodium clavatum (Stockmarr, 1971) was added to each sample in order to determine the pollen concentration (grains cm-3). Despite the unequal sedimentation rate, we used the radiocarbon ages to calculate the pollen accumulation rate (grains cm-2 year-1). Subsequently, the samples were mounted in glycerin gelatin. A minimum of 300 pollen grains of terrestrial flowering plants were counted. Spores of Pteridophyta and mosses were excluded from the total pollen sum. Pollen and spore identification was based on comparison with reference slides available at the Department of Palynology and Climate Dynamics of the University of Göttingen and morphological descriptions by Behling (1993). The Melastomataceae group did not include Combretaceae pollen because of the absence of this family in the local vegetation, supported by the
